Double ropes are independently rated to take a leader fall. That is, one strand of the rope can support a fall(s). You use them by clipping protection alternately, or at least in a way that reduces rope drag.

Twin ropes are often a bit thinner, and are NOT rated to take a fall on a single strand. They should both always be clipped to every piece of protection, just like a single rope.

In the central/eastern alps, twin ropes are more popular than double ropes. My double ropes are about ready to retire and I think I'll replace them with twins. They are really convenient, as long as you can avoid twisting them in knots at belays. No matter what I tell my various partners about alternating clipping, they just always clip both ropes to each piton. May as well just make it official.

Double ropes are great on trad terrain, especially where the lines wander. You can save a LOT of slings and rope drag, as the two lines can end up several meters apart from each other on a wandering pitch. No problem.

If you tell me more what you are considering either for.....I could probably help you if you are trying to chose between the two systems. I own all three systems and employ all three systems, all the time, depending on what the route needs are. Cheers.

MVS has got it right, however, I prefer halfs for the following reasons;

Half ropes have lower impact forces than twins, something to consider when ice climbing or when pro is questionable e.g alpine routes,Half ropes are far better suited for three person alpine climbing teams.A half rope can be used as a single on moderate terrainPrusiking a twin rope is even harder than twin due to rope stretch.

For the last three reasons, I go with a fairly burly half rope, an 8.5 mm Sharp Everdry, but in a shorter length, 50 meters. I rarely find them too short and are easier tor handle than 60 meter cords. In areas where the raps are fixed for double 60s, in which case 60s would be better, but in the 'pine 50s work great.

Thanks everyone for elaboration/improvement! On chossy or exploratory stuff, the lower impact force on gear provided by double ropes is a real comfort. Between those two systems, doubles are definitely the most versatile. My move towards twins recently is because I've been climbing more routes with straighter lines and predominately fixed protection.

Advocating taking a single rope on a multipitch route was something that would get you chewed out by at least one prominent Summitposter until recently! If you do this, you need a static rap line too, unless you want to lose your rack to attrition on the one time you have an unexpected retreat. I love climbing on a single rope, especially when the difficulty varies greatly. It's easier to switch to simul-climbing or soloing as needed. But I always had a static 50 meter line in a pack...and still felt nervous about it.

Twins are often used for ice. Though it seems like modern ice climbers don't just climb "pure ice" anymore. It won't be long before you are climbing some mixed pitches between ice sheet or pillar pitches. There, doubles would shine.

I know folks like to climb on really long single ropes too (like 70 meters). This might change the equation a little bit, but I don't know enough to elaborate. My sole usage of 70 meter twins on an ice climb a few years ago was a bit harrowing due to an unexpected need to communicate (follower's tool broke on simul-climb, at the worst possible spot...such is life!) made impossible by the ridiculous distance. However, I know people swear by this system as it can cut pitch counts in half.

EDIT: oh yeah, I think there is a statistic that rockfall never fully cut both strands of a double/twin system, right? But there are plenty of stories where a single rope was just severed. Big blocks of ice have sharp edges, so...

Great feedback MVS. One thing that MVS alluded to is the single rope and tag line combo. The idea is you combine a light single line with a thin, static line that you can tie together for rappels. You leave the tag line in the pack or use it to haul difficult pitches, but climb soley on a single. This is a light and simple system, and is the best choice of aid pitches are anticipated. Rope management skills to keep the tag line from tangling are neccessary to make this system workable.

Whoa, speaking of ropes I was just in the climbing shop this morning and saw a Mammut 60 meter rope which was 8.9 mm. It was a SINGLE, a DOUBLE and a TWIN too! Jeez. Technology is messing up our neat tried and true categories... :p

mvs wrote:Whoa, speaking of ropes I was just in the climbing shop this morning and saw a Mammut 60 meter rope which was 8.9 mm. It was a SINGLE, a DOUBLE and a TWIN too! Jeez. Technology is messing up our neat tried and true categories... :p

It has actually been that way for quite some time. However, weight considerations (significant remote climbing objectives regarding ice and/or rock) still cause most of us working in the industry to continue to own three systems, matching the appropriate system for the appropriate objective.

In other words, two 7+ mil twins still weigh considerably less than 8.9 twins in grams per meter. Relative when slogging through waist deep snow to get to the base of a big ice route. Those of us who guide and crag a lot to stay in shape, prefer a 9+ mil single for durability sake vs anything thinner. 8+ mill makes for ideal halfs/doubles which despite weighing more than twins, allow for many more options in the remote backcountry, i.e. East Face of Pigeon in the Bugaboos. That being said, we would rather haul 8.0-8.3's around than 8.9's. On multi day climbing trips, we count the weight on our backs in grams. That is why so many bivy and stove makers continue to shave off what can appear to be insignificant amounts of weight to those who are not climbing with it on their backs.

OK, I have to expose my soft underbelly. I'm not a climber, nor do I play one on TV. I once swore a solemn oath that I would never own a dynamic rope. I'm usually OK climbing short mid-5 sections without protection. I hate carrying rope. I rarely go up anything where there would be more than one "pitch" of more than 40'.

But now longer pitches are coming up. It's still really easy stuff for most of you, technical-wise, but at the end of 5000' gains with time restrictions... and I wonder, what are the smart, light rope choices?

To be concrete: I'm thinking of the ladder pitch on Baboquivari. Not dead vertical; a fall would likely start as a slide... but people have died from falls on the pitch. While it's rated 5.6, most folks tell me that it is "hard" for only about 20', then low class 5 or even 3-4. A 60m rope is recommended for a double-rope rap. There are about 3 places to clip in to ancient hangers on the way; BUT part of the "balance" when worrying about the rope, is that the old bolts might not stand high-impact falls anyway.

So I've thought:1) two 30m Eidelweiss twin ropes, 8mm, share the pain by giving one to another person in the party;2) one 30m 8.1 mm rope rated as a double (just very slightly heavier than the Eidelweiss, but a less abrasion resistant sheath), plus 30m of 6mm stiff pull cord (lots of Canyoneering friends...)